Philip J. Miller

Effects of pressure on the thermal decomposition kinetics, chemical reactivity and phase behavior of RDX

Abstract The effedts of pressure on the thermal decomposition kinetics, chemical reactivity, and phase behavior of RDX have been studied by a combination of measurement techniques in conjunction with a high-pressure diamond anvil cell. These techniques include (1) Fourier transform infrared (FTIR) spectroscopy for kinetic measurements and phase identification, (2) energy dispersive x-ray powder diffraction for identification of the observed polymorphic forms and also compression measurements, and (3) optical polarizing microscopy for visual detection and confirmation of phase transformations and determinations of transition pressures. The ruby method of pressure measurement was used in all methods employed. Studies were generally limited to the region where decomposition rates could be measured within reasonable laboratory time, i.e., below 10 GPa and 573 K. The P-T phase diagram for RDX was determined to 573 K and 7.0 GPa, delineating the stability fields of three solid phases, α, β, and γ, and the liquids. The α and β phases of RDX were found to thermally decompose, while the γ phase transformed to either α or β before reaching decomposition temperatures. The decomposition rate of α phase was found to increase with increasing pressure, suggesting a bimolecular-type mechanism. An activation energy of 51 kcal/mol and activation volume of −5.6 cm3/mol were calculated for the thermal decomposition reaction of α RDX.

Vibrational Spectroscopic Studies of Alane

ABSTRACT Alane has been subjected to Raman studies under static compression. The Raman spectra showed four modes, which increased in frequency as pressure was increased from ambient to 6.6 GPa. From the pressure dependence, the pressure coefficient, dνi/dP, for each mode has been estimated and used to evaluate the mode Grüneisen parameter γi for that mode. Independently the thermodynamic Grüneisen parameter γth has also been calculated using the pressure derivative of the isothermal bulk modulus value from the literature. Preliminary infrared spectra were also collected under ambient conditions and are discussed with those reported in the literature for alane polymorphs.

Shock wave and detonation wave response of selected HMX based research explosives with HTPB binder systems

The sensitivity, detonation properties, and performance of selected HMX based explosives are compared. All explosives were manufactured using a hydroxyl‐terminated polybutadiene (HTPB) binder system. IRX class explosives were manufactured to obtain explosives in which ingredients were systematically varied. The particle size range of the HMX particles was controlled by sieving. Sensitivity and performance experiments were conducted using the explosives IRX‐1, and IRX‐3A. These experiments measured: detonation pressure, detonation velocity, modified gap test shock sensitivity, and detonation wave curvature. Modified gap tests were also performed for SW‐21 and PBXN‐110. In addition, light gas gun experiments were performed in which reactive stress‐time profiles were obtained for IRX‐1 and PBXN‐110.

Pressure/Temperature/Reaction Phase Diagrams for Several Nitramine Compounds

Pressure/temperature/reaction phase diagrams for several nitramine compounds, including hexanitrohexaazaisowurtzitane (HNIW), 1,3,5-trinitrohexahydro-l,3,5-triazine (RDX), ammonium dinitramide (ADN), and p-nitroaniline (PNA) are presented. A diamond anvil cell was used in conjunction with optical polarizing light microscopy (OPLM), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray diffraction (EDXD), and micro FT-Raman spectroscopy to determine these diagrams. A description is given of the diamond anvil cell and the associated techniques employed.

Effects of Pressure on the Thermal Decomposition Rates, Chemical Reactivity and Phase Behavior of HMX, RDX and Nitromethane

The effects of pressure on the thermal decomposition kinetics, chemical reactivity and phase behavior of β HMX, RDX and nitromethane have been studied by a combination of measurement techniques in conjunction with a high pressure diamond anvil cell. These techniques include: (1) Fourier transform infrared (FTIR) spectroscopy, (2) energy dispersive x-ray powder diffraction, (3) optical polarizing microscopy, and (4)Raman scattering. Studies were generally limited to the region where decomposition rates could be measured within reasonable laboratory time, i. e., below 10 GPa and 573K. The P-T phase diagram for RDX was determined to 573K and 7.0 GPa, delineating the stability fields of three solid phases, α, β and γ, and the liquidus. The α and β phases of RDX were found to thermally decompose, while the γ phase transformed to either α or β before reaching decomposition temperatures. The decomposition rate of a phase was found to increase with increasing pressure suggesting a bimolecular-type mechanism. Conversely, β HMX decomposition rates decrease with increasing pressure suggesting a unimolecular-type reaction mechanism. Activation energies, volumes and entropies for the thermal decomposition reactions are calculated from the observed data for β HMX and α RDX. The decomposition mechanism for nitromethane appears to be complex and varies over large changes in pressure. A mechanism is proposed which explains the bimolecular nature of the reaction and also accounts for the observed pressure dependence of the decomposition rate and products.

Effects of late chemical reactions of the energy partition in non‐ideal underwater explosions

The bubble oscillation and the pressure pulse induced in the water due to the underwater detonation of nonideal explosives are calculated. In non‐ideal explosives, a substantial amount of energy could be released after the Chapman‐Jouguet surface, often after the bubble has expanded a few times the original charge size. The calculations were performed using a modified version of DYNA2D hydrocode in which a time‐dependent Jones‐Wilkins‐Lee equation of state was introduced in order to account for this late energy release. The effect of delaying the energy release on how the explosive chemical energy is partitioned between water and bubble is obtained.

The Diamond Anvil Cell for Physical and Chemical Investigations of Energetic Materials at High Pressures

Brief descriptions of the five generic types of diamond anvil high pressure cells are given with an assessment of their strengths and weaknesses for various kinds of scientific measurement applications. Three techniques applied successfully to the study of energetic materials, optical polarizing microscopy, infrared absorption spectroscopy, and energy dispersive x-ray powder diffraction, are described along with examples of some relevant data and results.

Effects of pressure on the structure and the thermal decomposition kinetics of RDX

Abstract High pressure and temperature structural changes for RDX were investigated to 7.0 GPa and 570 K in a diamond anvil cell apparatus using FTIR absorption, optical microscopy, and energy-dispersive powder x-ray diffraction techniques. Three distinct solid phases were observed. The effects of pressure on the thermal decomposition kinetics as a function of RDX pressure were investigated using an infrared absorption technique. Solid phase I was found to have a pressure enhanced reaction rate with an energy and volume of activation of 51 Kcal/mole and -5.6 cc/mole respectively. Solid II was not observed to react and the observed reaction rate of Solid III decreased with increasing pressure.